#!/bin/bash
#
# Developed by Fred Weinhaus 10/29/2008 .......... revised 1/25/2020
#
# ------------------------------------------------------------------------------
# 
# Licensing:
# 
# Copyright © Fred Weinhaus
# 
# My scripts are available free of charge for non-commercial use, ONLY.
# 
# For use of my scripts in commercial (for-profit) environments or 
# non-free applications, please contact me (Fred Weinhaus) for 
# licensing arrangements. My email address is fmw at alink dot net.
# 
# If you: 1) redistribute, 2) incorporate any of these scripts into other 
# free applications or 3) reprogram them in another scripting language, 
# then you must contact me for permission, especially if the result might 
# be used in a commercial or for-profit environment.
# 
# My scripts are also subject, in a subordinate manner, to the ImageMagick 
# license, which can be found at: http://www.imagemagick.org/script/license.php
# 
# ------------------------------------------------------------------------------
# 
####
#
# USAGE: otsuthresh [-g graph] infile outfile
# USAGE: otsuthresh [-help]
#
# OPTIONS:
#
# -g	  graph             graph specifies whether to generate a 
#                           histogram graph image displaying the 
#                           location and value of the threshold;
#                           choices are: view or save; 
#                           default is no graph
#
###
#
# NAME: OTSUTHRESH
# 
# PURPOSE: To automatically thresholds an image to binary (b/w) format 
# using Otsu's between class variance technique.
# 
# DESCRIPTION: OTSUTHRESH automatically thresholds an image to binary
# (b/w) format. It assume the histogram is bimodal, i.e. is the composite
# of two bell-shaped distributions representing the foreground and
# background classes. The Otsu appoach computes the Between Class Variance 
# from the foreground (above threshold data) and background (at and below 
# threshold value) for every possible threshold value. The optimal threshold 
# is the one that maximizes the Between Class Variance. This is equivalent 
# to finding the threshold that minimizes the overlap between the two 
# bell-shaped class curves.
# 
# OPTIONS: 
# 
# -g graph ... GRAPH specifies whether to generate a graph (image) of 
# the histogram, displaying the location and value of the threshold. 
# The choices are: view, save and none. If graph=view is selected, the 
# graph will be created and displayed automatically, but not saved. 
# If graph=save is selected, then the graph will be created and saved 
# to a file using the infile name, with "_histog_otsu.gif" appended,  
# but the graph will not be displayed automatically. If -g option is 
# not specified, then no graph will be created.
# 
# NOTE: It is highly recommended that the output not be specified 
# as a JPG image as that will cause compression and potentially a 
# non-binary (i.e. a graylevel) result. GIF is the recommended 
# output format.
# 
# REFERENCES: see the following:
# http://www.ph.tn.tudelft.nl/Courses/FIP/noframes/fip-Segmenta.html
# http://homepages.inf.ed.ac.uk/rbf/CVonline/LOCAL_COPIES/MORSE/threshold.pdf
# http://www.cse.unr.edu/~bebis/CS791E/Notes/Thresholding.pdf
# http://www.ifi.uio.no/in384/info/threshold.ps
# http://www.supelec.fr/ecole/radio/JPPS01.pdf
# 
# CAVEAT: No guarantee that this script will work on all platforms, 
# nor that trapping of inconsistent parameters is complete and 
# foolproof. Use At Your Own Risk. 
# 
######
#

# set default values
graph=""		#none, save or view

# set directory for temporary files
dir="."    # suggestions are dir="." or dir="/tmp"

# set up functions to report Usage and Usage with Description
PROGNAME=`type $0 | awk '{print $3}'`  # search for executable on path
PROGDIR=`dirname $PROGNAME`            # extract directory of program
PROGNAME=`basename $PROGNAME`          # base name of program
usage1() 
	{
	echo >&2 ""
	echo >&2 "$PROGNAME:" "$@"
	sed >&2 -e '1,/^####/d;  /^###/g;  /^#/!q;  s/^#//;  s/^ //;  4,$p' "$PROGDIR/$PROGNAME"
	}
usage2() 
	{
	echo >&2 ""
	echo >&2 "$PROGNAME:" "$@"
	sed >&2 -e '1,/^####/d;  /^######/g;  /^#/!q;  s/^#*//;  s/^ //;  4,$p' "$PROGDIR/$PROGNAME"
	}


# function to report error messages
errMsg()
	{
	echo ""
	echo $1
	echo ""
	usage1
	exit 1
	}


# function to test for minus at start of value of second part of option 1 or 2
checkMinus()
	{
	test=`echo "$1" | grep -c '^-.*$'`   # returns 1 if match; 0 otherwise
    [ $test -eq 1 ] && errMsg "$errorMsg"
	}

# test for correct number of arguments and get values
if [ $# -eq 0 ]
	then
	# help information
   echo ""
   usage2
   exit 0
elif [ $# -gt 4 ]
	then
	errMsg "--- TOO MANY ARGUMENTS WERE PROVIDED ---"
else
	while [ $# -gt 0 ]
		do
			# get parameter values
			case "$1" in
		  -h|-help)    # help information
					   echo ""
					   usage2
					   exit 0
					   ;;
				-g)    # get  graph
					   shift  # to get the next parameter
					   # test if parameter starts with minus sign 
					   errorMsg="--- INVALID GRAPH SPECIFICATION ---"
					   checkMinus "$1"
					   graph="$1"
					   [ "$graph" != "view" -a "$graph" != "save" ] && errMsg "--- GRAPH=$graph MUST BE EITHER VIEW OR SAVE ---"
					   ;;
				 -)    # STDIN and end of arguments
					   break
					   ;;
				-*)    # any other - argument
					   errMsg "--- UNKNOWN OPTION ---"
					   ;;
		     	 *)    # end of arguments
					   break
					   ;;
			esac
			shift   # next option
	done
	#
	# get infile and outfile
	infile="$1"
	outfile="$2"
fi

# test that infile provided
[ "$infile" = "" ] && errMsg "NO INPUT FILE SPECIFIED"

# test that outfile provided
[ "$outfile" = "" ] && errMsg "NO OUTPUT FILE SPECIFIED"

# get outname from infile to use for graph
if [ "$graph" != "" ]; then
	inname=`convert "$infile" -format "%t" info:`
	histfile=${inname}_histog_otsu.gif
fi

tmpA1="$dir/otsuthresh_1_$$.mpc"
tmpA2="$dir/otsuthresh_1_$$.cache"
trap "rm -f $tmpA1 $tmpA2; exit 0" 0
trap "rm -f $tmpA1 $tmpA2 $histfile; exit 1" 1 2 3 15

# get im_version
im_version=`convert -list configure | \
	sed '/^LIB_VERSION_NUMBER */!d; s//,/;  s/,/,0/g;  s/,0*\([0-9][0-9]\)/\1/g' | head -n 1`

# colorspace RGB and sRGB swapped between 6.7.5.5 and 6.7.6.7 
# though probably not resolved until the latter
# then -colorspace gray changed to linear between 6.7.6.7 and 6.7.8.2 
# then -separate converted to linear gray channels between 6.7.6.7 and 6.7.8.2,
# though probably not resolved until the latter
# so -colorspace HSL/HSB -separate and -colorspace gray became linear
# but we need to use -set colorspace RGB before using them at appropriate times
# so that results stay as in original script
# The following was determined from various version tests using otsuthresh.
# with IM 6.7.4.10, 6.7.6.10, 6.7.8.10
if [ "$im_version" -lt "06070607" -o "$im_version" -gt "06070707" ]; then
	setcspace="-set colorspace RGB"
else
	setcspace=""
fi
# no need for setcspace for grayscale or channels after 6.8.5.4
if [ "$im_version" -gt "06080504" ]; then
	setcspace=""
fi


if convert -quiet "$infile" $setcspace -colorspace gray +repage "$tmpA1"
	then
	: ' do nothing '
else
	errMsg "--- FILE $infile DOES NOT EXIST OR IS NOT AN ORDINARY FILE, NOT READABLE OR HAG ZERO SIZE ---"
fi	

# get totpix in image
width=`convert $tmpA1 -format "%w" info:`
height=`convert $tmpA1 -format "%h" info:`
totpix=`echo "scale=0; $width * $height / 1" | bc`

	# get value array from IM histogram
	valueArr=(`convert $tmpA1 -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- \
	| sed -n 's/[ ]*\([0-9]*\).*gray[(]\([0-9]*\).*$/\1 \2/p' |\
	awk '
	# AWK 
	{ vbin[$2] += $2;} 
	END { for (i=0;i<256;i++) {print vbin[i]; } } '`)
#	echo ${valueArr[*]}
#	echo ${#valueArr[*]}
	numvals=${#valueArr[*]}
	
	# get count array from IM histogram
	countArr=(`convert $tmpA1 -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- \
	| sed -n 's/[ ]*\([0-9]*\).*gray[(]\([0-9]*\).*$/\1 \2/p' |\
	awk '
	# AWK 
	{ cbin[$2] += $1; } 
	END { for (i=0;i<256;i++) {print cbin[i]; } } '`)
#	echo ${countArr[*]}
#	echo ${#countArr[*]}
	numcounts=${#countArr[*]}
	
	[ $numvals -ne $numcounts ] && errMsg "--- NUMBER OF COUNTS IS NOT THE SAME AS NUMBER OF VALUES ---"
	
	# compute normalized count array
	ncountArr=( $(for ((i=0; i<$numcounts; i++)); do
	echo "$i ${countArr[$i]}"
	done |\
	awk -v totpix="$totpix" -v numcounts="$numcounts" '
	# AWK 
	{ bin[$1] = $2; }
	END { for (i=0;i<numcounts;i++) {print bin[i]/totpix; } } ') )
#	echo ${ncountArr[*]}
#	echo ${#ncountArr[*]}

	# get global mean from values and normalized counts
	mean=$( for ((i=0; i<$numcounts; i++)); do
	echo "$i ${valueArr[$i]} ${ncountArr[$i]}"
	done |\
	awk -v numcounts="$numcounts" '
	# AWK 
	{ vbin[$1] = $2; ncbin[$1] = $3; } 
	END { for (i=0;i<numcounts;i++) { mean += vbin[i]*ncbin[i]; } print mean } ' )
#	echo "mean=$mean"


#Generate Cumulative Arrays
# p=c(i)/N (normalized count or probability, p, at bin i)
# v=v(i) (graylevel at bin i)
# t=threshold bin
# n=p0=sum(c(i)/N)zeroth histogram moment => cumulative normalized count (from i=0 to t) = N(t)
# g=p1=sum(c(i)*v(i))=first histogram momement => cumulative normalized graylevel (from i=0 to t) = G(t)


	# compute nlowArr
	nlowArr=( $(for ((i=0; i<$numcounts; i++)); do
	echo "$i ${ncountArr[$i]}"
	done |\
	awk -v numcounts="$numcounts" '
	# AWK to generate a cumulative histogram 1D image...
	{ nlowbin[$1] = $2; } 
	END { for (i=0;i<numcounts;i++) { nlow += nlowbin[i]; print nlow } } ') )
#	echo ${nlowArr[*]}
#	echo ${#nlowArr[*]}

	# compute glowArr
	glowArr=( $( for ((i=0; i<$numcounts; i++)); do
	echo "$i ${valueArr[$i]} ${ncountArr[$i]}"
	done |\
	awk -v numcounts="$numcounts" '
	# AWK to generate a cumulative histogram 1D image...
	{ vlowbin[$1] = $2; nclowbin[$1] = $3; } 
	END { for (i=0;i<numcounts;i++) { glow += vlowbin[i]*nclowbin[i]; print glow } } ') )
#	echo ${glowArr[*]}
#	echo ${#glowArr[*]}


# Compute Threshold
# loop through histogram using normalized counts and values
# compute threshold by maximizing between class variance
# bcv=Nl*(Ml-M)^2 + Nh*(Mh-M)^2 = (M*Nl-Gl)^2/(Nl*(1-Nl))

# m=p1/p0=mean => M(t)=G(t)/N(t) 
# where Nh and Nl are normalized counts above and below threshold (zeroth moments, p0)
# Mh and Ml are means of pixels above and below threshold
# Gh and Gl are normalized cumulative graylevels (first moments, p1)
# ML=Gl/Nl
# above derived using
# Nh=(1-Nl) for normalized histogram
# Mh=(M-Ml*Nl)/(1-Nl) where M is overall mean of image


	# compute threshold
	#note: must stop at second to last bin so that nlow != 1 exactly or get divide by zero
	threshbin=$(for ((i=0; i<$numcounts; i++)); do
	echo "$i ${nlowArr[$i]} ${glowArr[$i]}"
	done |\
	awk -v numcounts="$numcounts" -v mean="$mean" -v bcvold=0 -v threshbin=0 '
	# AWK to compute entropy threshold...
	{ nlowbin[$1] = $2; glowbin[$1] = $3; } 
	END { for (i=0;i<(numcounts-1);i++) 
	{ dmean = (mean*nlowbin[i] - glowbin[i]); bcv = dmean*dmean/(nlowbin[i]*(1-nlowbin[i])); 
	if (bcv>bcvold) { bcvold=bcv; threshbin=i; } } print threshbin } ')
#	echo "threshbin=$threshbin"
	thresh=${valueArr[$threshbin]}
#	echo "thresh=$thresh"
	threshpct=`convert xc: -format "%[fx:100*$thresh/255]" info:`



# compute threshold graph x coord and threshold in percent
xx=$thresh
threshpct=`convert xc: -format "%[fx:100*$thresh/255]" info:`
#echo "xx=$xx; threshpct=$threshpct"


echo "Thresholding Image At $threshpct%"
convert $tmpA1 -threshold $threshpct% "$outfile"
echo ""


if [ "$graph" != "" ]; then
	convert $tmpA1 -define histogram:unique-colors=false histogram:- | \
		convert - -negate \
		-stroke red -strokewidth 1 -draw "line $xx,0 $xx,200" \
		-background gray -splice 0x30 \
		-fill white -stroke white -strokewidth 1 \
		-font ArialB -pointsize 24 \
		-draw "text 4,22 'threshold=$threshpct%'" -resize 50% \
		-bordercolor gray50 -border 5 \
		"$histfile"
fi

if [ "$graph" = "view" ]; then
	convert "$histfile" x:
	rm -f "$histfile"
fi

exit 0



